JP2000091198A - X-ray mask manufacturing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an error due to a temperature change from occurring by providing a mechanism for applying a static voltage to a conductor block and that for controlling the level of a static voltage being applied according to the output of a surface height measurement mechanism. SOLUTION: A conductor block 16 is arranged at a part that opposes the reverse side of a mask 17, and a high DC voltage is applied by a high-voltage power source 15. Then, when the pressure of a fluid 21 for making constant the temperature of the mask is equal to zero, the interval between the reverse side of the mask 17 and the conductor block 16 is set to a specific distance. The output of a sensor 27 for monitoring potential in the direction of the face normal line at the center of the mask 17 being mounted to a mask holder 19 is read by a control computer 28 to control the high-voltage power supply 15 along with the output of a pressure gauge 24 and to control potential being fed to the conductor block 16. Also, the temperature of the conductor block 16 is made constant and that of the mask 17 is made constant, thus reducing an error in length dimension due to thermal expansion and stabilizing a resist process that is sensitive to temperature, namely improving a short dimension accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for manufacturing a mask for X-ray exposure.

[0002]

2. Description of the Related Art As the degree of integration of circuit elements such as semiconductor devices increases, the circuit patterns of the LSI elements constituting the circuit elements become increasingly finer. Since the miniaturization of the pattern will eventually reach the resolution limit of a transfer device using ultraviolet rays currently used for pattern formation for mass production, development of a new pattern formation technology is required.

[0003] One of the candidates that can respond to this request is X
There is a line lithography technique. In the X-ray lithography technology, soft X-rays having a wavelength of about 1 nm are used for exposure, and SiN, SiC,
A pattern is formed by proximity exposure using a mask in which an equal-size transfer pattern made of an absorber such as a metal is formed on a support film having a thickness of 1 to 3 μm made of a light element such as diamond. At this time, as a method of forming a desired pattern on the mask, an etching mask layer is formed on the absorber, and a resist is applied thereon, and then the resist is formed into the desired pattern by using an electron beam drawing apparatus. Processing of
It is common practice to process the etching mask layer by etching based on this resist, and then process the absorber based on the processed etching mask.

Since the inside of the electron beam lithography apparatus is kept in a vacuum for the purpose of allowing an electron beam to pass therethrough, it has not heretofore been carried out to directly heat the object to be drawn via a fluid during electron beam lithography. . However, as described above, since a mask of the same magnification is used in X-ray lithography, higher precision of the mask is required. Therefore, a long dimension error due to thermal expansion and a resist finish due to a temperature change during writing. It is necessary to severely suppress dimensional errors and the like. Furthermore, X
When drawing a line mask, as described above, when the fluid is brought into contact with the back surface for constant temperature because of the fact that the mask is composed of a thin film of at most several μm, However, there is a problem that the shape is greatly deformed.

[0005]

As described above, when manufacturing a mask for X-ray lithography, which is required in accordance with the miniaturization of elements, in the electron beam drawing process,
It is necessary to maintain the temperature of the mask without deforming the mask in order to obtain a highly accurate mask.

An object of the present invention is to provide a method for manufacturing an X-ray mask satisfying the above-mentioned conditions, and to provide a method for forming a fine pattern by X-ray lithography.

[0007]

According to the present invention, in order to solve the above-mentioned problems, as a first method, a mechanism for measuring a surface height of a substrate to be drawn, and at least a region to be drawn of the substrate to be drawn are provided. A conductor block facing the back surface of the substrate, a mechanism for filling the working fluid between the substrate to be drawn and the conductor block, a mechanism for applying an electrostatic voltage to the conductor block, and according to an output of the surface height measurement mechanism. An X-ray mask manufacturing apparatus including an electron beam lithography apparatus having a mechanism for controlling the magnitude of the applied electrostatic voltage.

As a second method, a conductor block facing at least the back surface of the drawing area of the drawing substrate is arranged,
An electron beam lithography is performed while applying an electrostatic voltage to the conductor block so that the working fluid maintained at a constant temperature is filled between the substrate to be drawn and the conductor block and the surface height of the substrate to be drawn is within a predetermined range. By doing so, an X-ray mask is formed.

As a third method, in the first method,
An X-ray mask manufacturing apparatus is provided, wherein the conductor block is provided with a temperature maintaining mechanism.

[0010] As a fourth method, in the second method,
The constant temperature of the working fluid forms an X-ray mask by constant temperature of the conductor block.

As a fifth method, in the third method,
An X-ray mask manufacturing apparatus is provided, wherein the thermostating mechanism includes a mechanism for circulating a second working fluid and a mechanism for thermostating the second working fluid.

As a sixth method, in the fourth method,
The constant temperature of the working fluid, by using a constant temperature of the second working fluid, by constant temperature of the conductor block,
An X-ray mask is formed.

As a seventh method, in the first, third or fifth method, a mechanism for electrically connecting an electrode having a predetermined potential to the drawing surface of the substrate to be drawn is provided. An X-ray mask manufacturing apparatus is provided.

As an eighth method, in the second, fourth, or fifth method, electron beam lithography is performed by performing electron beam lithography while the drawing surface of the substrate to be drawn is electrically connected to a predetermined potential. Form a mask.

According to the present invention, it is possible to suppress the occurrence of errors due to temperature changes in the electron beam writing process, which influence the accuracy of the X-ray mask, and thus obtain a highly accurate X-ray mask. I can do it. Then, by performing transfer using the obtained mask, it is possible to form a fine pattern with high precision.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing the vicinity of a mask holder of an electron beam drawing apparatus used in one embodiment of the present invention.

A mask holder 19 is fixed on an XY stage 10 on which a biaxial laser interferometer is mounted in a detachable manner, similarly to a normal electron beam drawing apparatus. The mask 17 is connected to a mask holder 19 via an O-ring 18 made of rubber.
Is fixed by a clamp 20. Mask holder 19
Is connected to an inflow pipe 22 and an outflow pipe 23 of helium (He), which is a fluid for mask thermostat 21, a pressure gauge 24 is connected to the outflow pipe 23, and an inflow pipe 22 and an outflow pipe 23 are respectively connected to the outflow pipe 23. Flow control mechanisms 25a and 25b, each of which includes a flow control valve, are connected, and a mechanism is provided that controls the flow rate according to the output of the pressure gauge 24 and that the pressure of the fluid 21 in the mask holder is adjusted to be constant. . In the present embodiment, considering the thermal conductivity, He
Was set to 1 Torr, and the amount of He flowing out and in was set to about 10 cm 3 per minute.

The surface of the mask is configured such that the terminal 33 to which the conductive wire is connected comes into contact with the edge cut portion of the resist with an extremely weak contact force. (Usually a ground potential). A conductor block 16 is arranged in a portion facing the back surface of the mask, and has a structure in which a high DC voltage can be applied by a high voltage power supply 15. In the present embodiment, by making this DC high voltage the same as the DC high voltage applied to the electrostatic chuck,
Although the apparatus is simplified, an individual power supply may be connected. In the present embodiment, when the pressure of the mask temperature-maintaining fluid 21 is 0, that is, when no external force is applied, the distance between the mask back surface and the conductor block 16 is set to 0.5 mm. This setting is based on the following design.

As shown in FIG. 3, when two electrodes face each other at a distance d and a voltage V is applied between them, the electromagnetic force per unit area PE acting between the two electrodes is as follows. It becomes the size given by the formula.

PE = (QE) / S = ε {(V2) / (d2)} (1) where Q is the electric charge accumulated on the surface, E is the electric field between the electrodes,
S is the area of the opposing part of the electrode, and the relational expression E = V / d, Q = CV,
C = ε (S / d) (where C is the capacitance and ε is the dielectric constant). ε
Substitute the dielectric constant of vacuum: 8.85 × 10 * (-12) F / m as PE
Demands that the pressure equals 1 Torr of He previously set, V / d = 3.9 kV / mm, and if d is 0.5 mm, V becomes about 2 kV. It can be.

The mask holder 19 is provided with a sensor 27 for monitoring the displacement of the central portion of the mask in the surface normal direction, and the output of the sensor 27 is taken into a control computer 28.
By controlling the high-voltage power supply 15 in combination with the output of the pressure gauge 24, the potential applied to the conductor block 16 is controlled. Usually, the displacement of the X-ray mask surface is very sensitive to pressure, and the relational expression is given by the following expression (2).

P = {(4tσ0) / (r2)} h + {(8t) / (3r4)} {(E) / (1-ν)} h3 (2) where P is the pressure difference and h is the surface center , R is the radius of the thin film, σ0 is the film stress, t is the film thickness, E is the Young's modulus of the thin film, ν
Is the Poisson's ratio of the thin film. Note that, of course, the displacement of the film is maximum at the center. Therefore, in order to monitor the displacement with the highest sensitivity, it is desirable to monitor the displacement at the center. As an example, r = 35 mm, t = 2 μm, σ
Assuming 0 = 100 MPa, from equation (2), the amount of change in P corresponding to a small displacement of h near h is 0 is approximately 0.653 Pa /
It can be seen that μm = 4.90 mTorr / μm. On the other hand, from the above equation (1), {(ΔPE) (PE)} for small changes in PE and V
= 2 {(ΔV) / (V)} holds, so by controlling the applied voltage with an accuracy of about 0.1%, it becomes possible to control the PE with an accuracy of about 0.2%. About 2 mTorr
Can be controlled with a precision of. Therefore, the surface displacement is 0.4 μm
It can be seen that control can be performed with sufficient accuracy as follows.

In order to maintain the temperature of the mask, the fluid 21 for maintaining the temperature of the mask may be directly heated and cooled. However, in this embodiment, the temperature of the conductor block 16 is indirectly controlled. To keep the temperature constant. this is,
Mask constant temperature fluid 21 with good thermal conductivity but small heat capacity
This is because controlling the temperature of the conductor block 16 having a large heat capacity at a constant temperature is easier than directly heating and cooling. Although the Peltier element may be used to keep the temperature of the conductor block 16 constant, in the present embodiment, the working fluid 11 is used to keep the temperature constant. The working fluid 11 composed of pure water is circulated through a thermostat 26 outside the vacuum chamber, passes through the insulating flexible tube 12a, flows through the space provided in the conductor block 16 through the inflow port 13, and flows through the space. Via exit 14
It again circulates through another insulating flexible tube 12b. This mechanism allows the conductor block
Since the temperature of 16 can be kept constant, the X-ray mask substrate having a small heat capacity can be kept at a constant temperature via the mask constant-temperature fluid 21 having good heat conductivity. As a result, it is possible to reduce long dimension errors due to thermal expansion and to stabilize a temperature-sensitive resist process, that is, to improve short dimension accuracy.

On the other hand, in order to obtain a highly accurate mask, it is necessary to pay attention to the mask distortion. Specifically, when an uneven force is applied during mask clamping or electrostatic chucking, or when minute dust is interposed on the chuck surface, the mask is deformed,
It is known that positional distortion of several tens of nm easily occurs. In order to suppress this to the utmost, in the present invention, the lower surface of the mask is configured to be supported only by the contact portion with the O-ring 18, and the contact area is also reduced to the cross-sectional diameter of the O-ring like a normal O-ring. The load on the mask is limited so that the ring has a width not more than 1/3 of the cross-sectional diameter of the O-ring, instead of a ring having almost the same width. Further, it is desirable that the clamp 20 be located right above the contact portion with the O-ring in order to reduce distortion. More desirably, the clamp 20 is used only at the time of transportation or the like, and before starting drawing, the mask is attracted using only the electrostatic chuck, and drawing is performed with the clamp 20 opened. This is because mechanical clamps can easily distort the mask even if a slight displacement occurs due to assembly tolerances, whereas electrostatic chucks apply suction force evenly to the entire surface, so the mask This is because there is a characteristic that distortion is hardly given. The through-hole 29 provided outside the O-ring 18 is a place where a pin for pushing up the mask passes when the mask is attached / detached. Therefore, there is an advantage that the structure can be simplified.

FIG. 2 is a sectional view corresponding to an X-ray mask manufacturing process according to an embodiment of the present invention.

First, a 525 μm-thick 4 inch
Using a low-pressure CVD method for Si (100) wafer 1 (Fig. 2a),
At a substrate temperature of 1025 ° C and a pressure of 30 Torr, silane gas diluted with 10% hydrogen is 150 sccm and acetylene gas diluted with 10% hydrogen is used.
65 sccm and 150 sccm of 100% hydrogen chloride gas were introduced into the reaction tube together with 10 SLM of hydrogen as a carrier gas to form a 2 μm-thick SiC film to be the X-ray transparent thin film 2 (FIG. 2b). Next, a 98 nm-thick Al2O3 film serving as an anti-reflection film and an etching stopper 3 was formed on the surface of the substrate using an rf sputtering apparatus under the conditions of an Ar pressure of 1 mTorr (FIG. 2).
c).

On top of that, Ar sputtering was performed using an rf sputtering apparatus.
A 0.4 μm-thick tungsten (W) -rhenium (Re) alloy film serving as the absorber 4 is formed under the condition of a pressure of 3 mTorr, and an annealing process is performed after the formation to reduce the stress of the alloy film to approximately 0 MPa. Adjusted (FIG. 2d).

Further, the film thickness is set to 0.
A chromium (Cr) film serving as an etching mask layer 5 having a thickness of 05 μm was formed (FIG. 2E).

Then, using an RIE apparatus, an aluminum etching mask, a pressure of 10 mTorr, and an RF power of 200
Under the condition of W, a CF4 gas of 25 sccm and an O2 gas of 40 sccm were supplied to remove the SiC film in a central area of a back surface having a radius of 70 mm, thereby forming an opening area 6 serving as a back etching mask (FIG. 2F). . Next, a glass ring having an outer diameter of 125 mm, an inner diameter of 72 mm, and a thickness of 6.2 mm was joined as a frame 7 using an ultraviolet-curable epoxy resin adhesive to form a substrate (FIG. 2g). It should be noted that a thin film of Cr is vapor-deposited in advance on a plane that does not participate in the bonding of the glass ring to impart conductivity.

Using a back etching apparatus, a 1: 1 mixture of hydrofluoric acid and nitric acid was dropped into the portion where the SiC had been removed, and the Si was removed by etching (FIG. 2h).

On this substrate, a commercially available positive resist for electron beam ZEP-520 (viscosity: 12 cps) is spin-coated on the substrate under the conditions of a rotation speed of 2000 rpm and 50 seconds, edge-cut, and then using a hot plate. Bake at 175 ° C for 2 minutes,
A photosensitive film 8 having a thickness of 0.3 μm was formed (FIG. 2I).

Then, a pattern was drawn on this substrate by using an electron beam drawing apparatus with an acceleration voltage of 75 kV provided with the aforementioned mask holder. To obtain the desired drawing accuracy,
In the writing, multiple writing was performed to form a pattern by overwriting four times, and the proximity effect correction was performed by correcting the irradiation amount while setting the reference irradiation amount to 96 μC / cm 2. After drawing, development was performed using a commercially available developer ZEP-RD as a development process at a liquid temperature of 18 ° C. for 1 minute, followed by rinsing with MIBK for 1 minute to remove the developer (FIG. 2j). Based on the formed resist pattern, the Cr film 5 was processed by reactive ion etching using BCl3 and Cl2 gases (FIG. 2k). The remaining resist was removed by ashing in oxygen plasma. (FIG. 21) Finally, the processed Cr film 5 is used as an etching mask.
The W-Re alloy film 4 was processed by reactive ion etching using CHF3 and SF6 gases. (Figure 2m) Using the mask manufactured by the above process, the SOR light source was applied on a Si wafer using the exposure light with a center wavelength of 0.8 nm using a beam line with a mirror and a vacuum barrier Be film. When transferred to the resulting resist, a pattern with a line width of 70 nm could be formed. Good dimensional accuracy,
When the in-plane distribution of the transfer pattern dimensions was measured, a variation (3σ) of 7.3 nm was obtained for 20 measurement points.

It should be noted that the numerical values, materials, and the like shown in the present embodiment are merely examples, and can be applied to various cases without departing from the spirit of the present invention. For example, about 1 Torr of He gas was used for the mask temperature-regulating fluid.
A gas other than He, such as Ne, Ar, or N2, may be used, and any pressure can be used as long as the pressure is balanced with the electrostatic force. However, if the pressure is extremely low, the thermal conductivity will be remarkably reduced, and the constant temperature function will be impaired. Therefore, it is desirable that the pressure be approximately 50 mTorr or more. Furthermore, pure water was used as the working fluid used for maintaining the temperature of the conductor block, but other liquids such as oil and alcohol, gases such as N2 and dry air, or a heat medium known by the trade name Florinert were used. It is also possible to be. In this embodiment, the present invention is applied to an X-ray mask. However, the present invention may be applied to the manufacture of another mask, for example, a mask in the case of using a short wavelength ultraviolet light, an electron beam, an ion beam, or the like. It is possible.

[0035]

According to the present invention, it is possible to suppress the occurrence of an error due to a temperature change in the electron beam lithography process, which affects the accuracy of the X-ray mask, thereby obtaining a high-precision X-ray mask. I can do it. Then, by performing transfer using the obtained mask, it is possible to form a fine pattern with high precision.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment according to the present invention.

FIG. 2 is a sectional view showing an embodiment according to the present invention.

FIG. 3 is a cross-sectional view illustrating the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Deposition substrate (Si) 2 ... X-ray transmissive thin film (SiC) 3 ... Antireflection film and etching stopper (Al2O3) 4 ... Absorber (W-Re) 5 ... Etching mask layer (Cr) 6 Open area 7 Frame 8 Resist (photosensitive film) 10 Stage 11 Working fluid (pure water) 12 a, b Flexible tube 13 ... Inlet 14 ... Outlet 15 ... High voltage power supply 16 ... Conductor block 17 ... Mask 18 ... O-ring 19 ... Mask holder 20 ... Clamp 21 ... Mask isothermal fluid (He) 22 ・ ・ ・ Inflow pipe 23 ・ ・ ・ Outflow pipe 24 ・ ・ ・ Pressure gauge 25a, b ・ ・ ・ Flow rate adjustment mechanism 26 ・ ・ ・ Heat-retention device 27 ・ ・ ・ Sensor 28 ・ ・ ・ Control Computer 29: Through-hole 30: Insulating block 31・ Pump 32 ・ ・ ・ Valve 33 ・ ・ ・ Terminal 34 ・ ・ ・ Electronic optical system

Claims (8)

[Claims] 1. A mechanism for measuring a surface height of a substrate to be drawn, a conductor block facing at least a back surface of a region to be drawn of the substrate to be drawn, and a working fluid flowing between the substrate and the conductor block. An X-ray comprising an electron beam drawing apparatus having a mechanism for filling, a mechanism for applying an electrostatic voltage to the conductor block, and a mechanism for controlling the magnitude of the applied electrostatic voltage according to the output of the surface height measuring mechanism Mask manufacturing equipment. 2. A conductor block opposed to at least a back surface of a region to be drawn of a substrate to be drawn is arranged, and a working fluid maintained at a constant temperature between the substrate to be drawn and the conductor block is filled.
X for performing electron beam lithography while applying an electrostatic voltage to the conductor block so that the surface height of the substrate to be drawn is within a predetermined range.
Line mask manufacturing method. 3. The X-ray mask manufacturing apparatus according to claim 1, wherein the conductor block has a temperature-regulating mechanism. 4. The method for manufacturing an X-ray mask according to claim 2, wherein the constant temperature of the working fluid is performed by constant temperature of the conductor block. 5. The X-ray mask according to claim 3, wherein the constant temperature mechanism includes a mechanism for circulating a second working fluid and a mechanism for constant temperature of the second working fluid. manufacturing device. 6. The X-ray according to claim 4, wherein the working fluid is thermostated by using the thermostated second working fluid to thermostat the conductor block. Mask manufacturing method. 7. The X-ray mask manufacturing apparatus according to claim 1, further comprising a mechanism for electrically connecting an electrode having a predetermined potential to a drawing surface of the substrate to be drawn. . 8. The method of manufacturing an X-ray mask according to claim 2, wherein the drawing surface of the drawing target substrate is electrically connected to a predetermined potential to perform the electron beam drawing. .